Get a window back on normal level after put it on top level

[wazlid]

Hello guys!
On my window i have a checkbox button that allows me to put the window on top level when it is checked and on normal window when it is unchecked. This is how i am trying to reach that but it is not working.
Thanks for help!!

Qt::WindowFlags flags = this->windowflags();
       if(ui->istopLvlcheckBox->isChecked()){
           flags |= Qt::WindowStaysOnTopHint;
        }else{
            flags &= ~Qt::WindowStaysOnTopHint;
        }
        this->setWindowFlags(flags);
       this->show();

Qt::WindowFlags flags = this->windowflags();
       if(ui->istopLvlcheckBox->isChecked()){
           flags |= Qt::WindowStaysOnTopHint;
        }else{
            flags &= ~Qt::WindowStaysOnTopHint;
        }
        this->setWindowFlags(flags);
       this->show();

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